Rechargeable battery pack and battery pack charger with safety mechanisms

ABSTRACT

Rechargeable battery packs include one or more key slots along a rear edge in order to distinguish it from other battery pack types and rectangular guide tabs to be backward compatible with former battery pack chargers and former battery operated devices. Battery pack chargers include one or more key tabs in a door and rectangular guide tabs to differentiate rechargeable battery packs that can be safely charged. Door closure switches on a safety switch to activate safe charging of a rechargeable battery pack with matching one or more key slots. The one or more key tabs and the one or more key slots provide a safety mechanism to distinguish rechargeable battery packs which can be safely charged. Rectangular guide tabs on sidewalls of an inner housing allow rectangular guide tabs of the rechargeable battery packs to slide under and further differentiates those that can be safely charged.

FIELD OF THE INVENTION

[0001] This invention relates to battery charging systems and moreparticularly to battery chargers and rechargeable battery packs.

BACKGROUND OF THE INVENTION

[0002] Rechargeable batteries are well known in the prior art.Rechargeable batteries are capable of being charged prior to initial useand recharged after being discharged. Generally, rechargeable batteriesare charged by a battery charger having a power supply that can providea supply of DC current. A rechargeable battery accepts the electricalcurrent and converts it into chemical energy. As long as therechargeable battery is capable of converting the electrical currentinto chemical energy, the rechargeable battery will not significantlyrise in temperature. When a rechargeable battery is at full capacity, itis incapable of converting the charge current into chemical energy andit dissipates any continuing charge current as heat. The heat generatedby a rechargeable battery is an ideal parameter to sense that it hasreached a fully charged state.

[0003] One or more rechargeable batteries are oftentimes packed togetherin series as a rechargeable battery pack to provide a desiredoperational voltage and current. The rechargeable battery packs areoften used to power battery powered devices such as toys which areoftentimes operated by children. The rechargeable battery packs areremovable from a battery powered device for a number of reasons. Areason for providing a removable rechargeable battery pack is that onebattery pack can be remotely charged while another is being used in thebattery powered device. The typical rechargeable battery pack has one ormore rechargeable batteries coupled in series together. Two terminals ofthe rechargeable battery pack are coupled to each end terminal of theseries of rechargeable batteries. At least one end terminal of theseries of rechargeable batteries is typically coupled to one of theterminals of the battery pack by a wire. The rechargeable batteries areencased into a rechargeable battery case with a positive battery packterminal protruding through an opening in one side of the case and anegative battery pack terminal protruding through another opening in theother side of the case in order to make contact with charging terminalsof a battery pack charger. The rechargeable battery case is typicallymade of a plastic material that is insulating so as not to short tometal electrical contact points.

[0004] The typical rechargeable battery pack case is rectangularlyshaped. The typical width of a rechargeable battery pack case isapproximately the length of a rechargeable battery when rechargeablebatteries are oriented therein side by side without stacking. Thetypical length of a rechargeable battery pack case is approximately thesum of the diameters or widths of rechargeable batteries held within thecase for rechargeable batteries sitting side by side. On the left andright sides of the rechargeable battery pack case, there is a base edgeand a top edge. The base edge has a narrower region than the typicalwidth of the rechargeable battery pack case. To hold the rechargeablebattery pack into a battery powered device or battery charger, thetypical rechargeable battery pack case has multiple L shaped tabs alongthe base edge of one side and three mirrored-L shaped tabs along thebase edge of the opposite side. The multiple L shaped tabs and themultiple mirrored-L shaped tabs protrude from the narrower region of thebase edge to approximately have the typical width of the typicalrechargeable battery pack. The shape and foot of the L and mirrored-Lshaped tabs hold the battery pack in contact to the terminals of thebattery powered device or battery charger.

[0005] The typical battery pack charger has open faced surfaces tocouple with the rechargeable battery pack. The battery pack chargerincludes two opposing surfaces one having a positive electrical contactprotruding through it and another having a negative electrical contactprotruding through it. These electrical contacts are accessible to auser and typically do not have any safety concerns as the voltage onthese terminals is below 24 volts which is considered a safe voltage.This low voltage is typical of low current chargers in that an isolationtransformer is used to convert the 120 volt AC-line power into a lowervoltage that is typically 12 volts AC. Higher current power systems arerequired if a battery is to be charged at a higher rate, which means ahigher charge current. Higher current power supplies in some casescannot employ an isolation transformer to step the 120 volt AC-linepower down to a safe voltage. This is because an appropriate sizedisolation transformer may be very expensive, large and heavy. Without anisolation transformer, the terminals of the charger may be unsafe totouch because a high voltage may be present at the electrical contacts.Touching just one terminal can result in shock because a current may beable to travel from the non-isolated electrical contact of the chargerthrough a human body to ground.

[0006] When engaged, the rechargeable battery pack is not enclosed bythe typical battery pack charger. The surfaces of the rechargeablebattery pack are grabable by a user to engage or disengage it with thebattery pack charger. To engage with a battery pack charger, therechargeable battery pack is slid against a flat surface of the batterypack charger between the two opposing surfaces, orthogonal to the flatsurface and separated by the width of the rechargeable battery pack, inorder to make mechanical and electrical connections with the charger.The electrical and mechanical connections are made on the sides of therechargeable battery pack. One of the two opposing surfaces of thebattery pack charger has a negative electrical contact protrudingthrough side to make electrical connection to the contact on one side ofthe rechargeable battery pack and another one of the two opposingsurfaces has a positive electrical contact protruding through so as tomake electrical connection with the contact on the other side of therechargeable battery pack.

[0007] To make mechanical connections, the typical battery pack chargerincludes an upside down L shaped tab and an upside down mirrored-Lshaped tab in the respective opposing surfaces. The battery pack case ofthe rechargeable battery pack, uses the L and mirrored-L shaped tabsclosest to the terminals of its three L and mirrored-L shaped tabs tomate with the battery pack charger. The upside down L shaped tab of thebattery pack charger mates with the first mirrored-L shaped tab of therechargeable battery pack on one side. The upside down mirrored-L shapedtab of the rechargeable battery pack mates with the first L shaped tabof the rechargeable battery pack on the opposite side. The matingbetween these tabs, keeps the rechargeable battery pack from movingfurther forward, keeps it aligned with the electrical contacts and keepsthe rechargeable battery pack coupled in place to the battery packcharger in one direction.

[0008] To hold the rechargeable battery pack in place in an orthogonaldirection, the battery pack charger includes a spring loaded latchmechanism having a catch and a user push button. The spring loaded latchinterfaces to one side only of the rechargeable battery pack wheninserted. With the rechargeable battery pack being inserted, as thefirst mirrored-L shaped tab passes over the catch of the spring loadedlatch, the catch of the spring loaded latch is depressed into thecharger. After the end of the first mirrored-L shaped tab has passed,the catch of the spring loaded latch is released to protrude up behindthe first mirrored-L shaped tab in order to hold the rechargeablebattery pack to the battery pack charger. To release the rechargeablebattery pack from the battery pack charger, a user depresses the buttonof the spring loaded latch to depress the catch so the first mirrored-Lshaped tab can clear the catch as the rechargeable battery pack ispulled away by a user from the battery pack charger.

[0009] A typical low-cost battery charger provides a charging currentthat is a relatively low current to a rechargeable battery such that itcan be sustained indefinitely without damaging the battery. This lowcurrent, typically between 25 milliamps and 100 milliamps, will safelycharge a battery from a discharged state to a fully charged state inapproximately 4 to 12 hours. This low current provided by the low costbattery charger is sometimes referred to as a trickle charge. Thetrickle charge current can be set to a level where the battery cansafely dissipate excess current into heat without overheating thebattery. Generation of excessive heat in a rechargeable battery willcause it to breakdown and reduce its useful lifetime. A disadvantage tousing a low current and low cost battery charger is that it requirescharging a battery for a relatively long period of time in order toreach a fully recharged state.

[0010] Rechargeable batteries in a rechargeable battery pack can becharged at higher rates using higher current levels than that used atslow charge rates. However when fast charging, safety precautions shouldbe taken to prevent overheating of the batteries thereby preventing apossible fire, injury to a user, or damage to the battery or the batterycharger. Preventing injury to a user is particularly important when acharging system is utilized by children to recharge batteries that areutilized in toys. Additionally, as new fast charge technology is appliedto rechargeable batteries for use within toys, safety precautions becomevery important as a result. If no safety precautions are taken, thenrechargeable battery packs should only be charged at slow rates usinglow current levels.

[0011] Some safety precautions for fast charging that can be taken is toassure that a battery charger will not charge a rechargeable battery atan excessively high rate and that the charging current is removed orreduced, such as to a trickle charge rate, shortly after the batteryreaches its fully charged state. The charge rate refers to the level ofcharge current and the time to recharge a discharged battery. A chargerate is excessive if it exceeds the rate at which a rechargeable batterycan convert the charge current into chemical energy. This occurs whenthe charging current level is higher than the maximum charge currentrated for a given battery type and capacity. For example, a typical 50milliamp-hour Nickel-Cadmium (NiCad) battery can safely be charged up toa charging current level of 200 milliamps while a 700 milliamp-hourNiCad battery can be safely charged up to a charging current level of2.8 amps. Typically, NiCad battery construction will allow for a batterycell to be recharged at two to ten times its hour rating of batterycapacity. Battery manufacturing techniques vary from manufacturer tomanufacturer as well as from cell type to cell type which dictates themaximum charge rate for each cell. If the charge rate is excessive, thebattery produces heat to dissipate the energy provided by the excessivecharge current level. Regardless of the charge current level, when abattery reaches its fully charged state it is no longer capable ofconverting the charge current into chemical energy. In this case, thebattery dissipates the extra charge current as heat and the currentshould be removed or reduced such as to a trickle charge current inorder to avoid damage, maintain battery life, and protect persons andproperty from harm.

[0012] It is desirable to provide a fast charge battery charging systemhaving safety features to avoid damage, maintain battery life, andprotect persons and property from harm.

BRIEF SUMMARY OF THE INVENTION

[0013] The present invention includes the methods, systems and apparatuswhich are briefly summarized in the claims.

[0014] Briefly, a battery charging system including a rechargeablebattery pack and a battery pack charger is disclosed. The rechargeablebattery pack and the battery pack charger include mechanical safetymechanisms to safely charge the rechargeable battery pack using at leastone fast charge rate. The rechargeable battery pack and the battery packcharger are mechanically and electrically coupled together in order tocharge the rechargeable battery pack.

[0015] The rechargeable battery pack includes an opening to allow atemperature sensor to directly sense the temperature at a terminal caseof a rechargeable battery cell in the rechargeable battery pack. Atemperature sensor is used to determine when to automatically cutoffcharging at the at least one fast charge rate. The rechargeable batterypack further includes one or more key slots along a rear edge in orderto distinguish it from others. Additionally, rectangular guide tabs inthe rechargeable battery pack of the present invention allow it to bebackward compatible. The rechargeable battery pack of the presentinvention can be charged in former battery pack chargers and used topower former battery operated devices.

[0016] The battery pack charger includes one or more key tabs in acharger door that need to mate with the one or more key slots in therechargeable battery pack in order for the charger door to close into aclosed position and begin charging. The combination of the one or morekey tabs with the one or more key slots provides a safety mechanism toassure that the appropriate battery pack is inserted which can be safelycharged.

[0017] The battery pack charger further includes a high current chargerpower supply which is not electrically isolated from AC line power. Thebattery pack charger due to the non-isolated power supply designincludes a safety switch mechanism that facilitates the safety systemprovided by the key slots in the battery pack and tabs on the chargingdoor to avoid electrical shock to a user in the event that a usertouches one of the charging terminals when a rechargeable battery packis not inserted into the charger. The safety switch mechanism includesat least one switch to switch one circuit or a pair of switches toswitch two circuits. In one embodiment the switch (or pair of switches)is a spring switch with a leaf spring contact or button. In anotherembodiment, the switch (or pair of switches) is a micro-switch with aleaf spring lever activation. In yet another embodiment, the switch (orpair of switches) is formed of a conductive strip and a spring loadedconductive strip. One lever arm or and a pair of lever arms of thecharger door of the battery pack charger are used to activate the safetyswitch mechanisms. The one or more lever arms activate (i.e. close, turnON or switch ON) and deactivate the one or more switches (i.e. open,turn OFF or switch OFF) by applying or releasing a pressure or force ona contact point of the leaf spring contact, the button, the leaf springlever, or the spring loaded conductive strip. When the charger door isclosed, the lever arms push on the leaf spring contact, the button, theleaf spring lever, or the spring loaded conductive strip in order toclose the switch to provided a closed circuit. With the charger door inan open position there is no pressure from the lever arm on the leafspring contact, the button, the leaf spring lever, or the spring loadedconductive strip. Therefore, the safety switches are not closed andprovide an open circuit when the charger door is in the open position.When the charger door is in a closed position, the closing of the safetyswitch mechanism (or mechanisms) allows power to be supplied to arechargeable battery pack that is inserted into the battery packcharger.

[0018] The battery pack charger further provides rectangular guide tabson sidewalls of an inner housing that allow the rectangular guide tabsof the rechargeable battery pack to slide under. The rectangular guidetabs of the battery pack charger further distinguish the type ofrechargeable battery packs that can be fully inserted therein for safecharging.

[0019] The battery pack charger further includes a charger power supplyon a printed circuit board with the appropriate circuitry to charge therechargeable battery pack at the at least one fast charge rate. Thebattery pack charger includes a temperature sensor coupled to theprinted circuit board at one end that reaches through the opening in therechargeable battery pack to directly sense battery temperature at aterminal case of a rechargeable battery cell in the rechargeable batterypack.

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0020]FIG. 1 is a front perspective view from above of a firstembodiment of our new design for a rechargeable battery pack;

[0021]FIG. 2 is a rear perspective view from below thereof;

[0022]FIG. 3 is a top plan view thereof;

[0023]FIG. 4 is a right side elevational view thereof;

[0024]FIG. 5 is a bottom plan view thereof;

[0025]FIG. 6 is a left side elevational view thereof;

[0026]FIG. 7 is a front elevational view thereof;

[0027]FIG. 8 is a rear elevational view thereof;

[0028]FIG. 9 is a rear elevational view of a second embodiment of ournew design for a rechargeable battery pack; and

[0029]FIG. 10 is a top plan view thereof.

[0030]FIG. 11 is a front perspective exploded view from the top of thefirst embodiment of the rechargeable battery pack of the presentinvention.

[0031]FIG. 12 is a bottom perspective view of the battery pack chargerof the present invention.

[0032]FIG. 13 is a perspective view illustrating the battery packcharging system of the present invention.

[0033]FIG. 14 is an left side exploded view of the battery pack chargerof the present invention.

[0034]FIG. 15 is a bottom sectional view of a first embodiment for thecharger door of the battery pack charger to mate with the firstembodiment of the rechargeable battery pack.

[0035]FIG. 16 is a bottom sectional view of a second embodiment for thecharger door of the battery pack charger to mate with the secondembodiment of the rechargeable battery pack.

[0036]FIG. 17 is a top sectional view of the battery pack charger of thepresent invention.

[0037]FIG. 18 is a top sectional magnified view of the temperaturesensor of the battery pack charger probing the temperature of a batteryin the rechargeable battery pack.

[0038]FIG. 19 is a right side cut-away sectional view of the batterypack charger with an open charger door to receive the rechargeablebattery pack.

[0039]FIG. 20 is a right side cut-away sectional view of the batterypack charger with the rechargeable battery pack inserted therein.

[0040]FIG. 21 is a right side cut-away sectional view of an alternateembodiment of the battery pack charger with an open charger door toreceive the rechargeable battery pack.

[0041]FIG. 22 is a right side cut-away sectional view the alternateembodiment of the battery pack charger with the rechargeable batterypack inserted therein.

[0042]FIG. 23 is a top sectional view of the alternate embodiment of thebattery pack charger of the present invention.

[0043]FIG. 24 is a simplified schematic block diagram representation ofthe electronics of the battery pack charger of the present invention.

[0044] The rechargeable battery pack is used to store an electric chargeor energy and may be inserted into a battery pack charger or a batterypowered device.

[0045] The broken lines shown in FIGS. 1 and 2 are for illustrativepurposes only and form no part of the first or second embodiment of ournew design for a rechargeable battery pack.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0046] In the following detailed description of the present invention,numerous specific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be obvious toone skilled in the art that the present invention may be practicedwithout these specific details. In other instances well known methods,procedures, components, and circuits have not been described in detailso as not to unnecessarily obscure aspects of the present invention.

[0047] Briefly, a battery charging system including a rechargeablebattery pack and a battery pack charger is disclosed. The rechargeablebattery pack and the battery pack charger include mechanical safetymechanisms to safely charge the rechargeable battery pack using at leastone fast charge rate. The rechargeable battery pack and the battery packcharger are mechanically and electrically coupled together in order tocharge the rechargeable battery pack.

[0048] The rechargeable battery pack includes an opening to allow atemperature sensor to directly sense the temperature at a terminal caseof a rechargeable battery cell in the rechargeable battery pack. Atemperature sensor is used to determine when to automatically cutoffcharging at the at least one fast charge rate. The rechargeable batterypack further includes one or more key slots along a rear edge in orderto distinguish it from others. Additionally, rectangular guide tabs inthe rechargeable battery pack of the present invention allow it to bebackward compatible. The rechargeable battery pack of the presentinvention can be charged in former battery pack chargers and used topower former battery operated devices.

[0049] The battery pack charger includes one or more key tabs in acharger door that need to mate with the one or more key slots in therechargeable battery pack in order for the charger door to close into aclosed position and begin charging. The combination of the one or morekey tabs with the one or more key slots provides a safety mechanism toassure that the appropriate battery pack is inserted which can be safelycharged.

[0050] The battery pack charger further includes a high current chargerpower supply which is not electrically isolated from AC line power. Thebattery pack charger due to the non-isolated power supply designincludes a safety switch mechanism that facilitates the safety systemprovided by the key slots in the battery pack and tabs on the chargingdoor to avoid electrical shock to a user in the event that a usertouches one of the charging terminals when a rechargeable battery packis not inserted into the charger. The safety switch mechanism includesat least one switch to switch one circuit or a pair of switches toswitch two circuits. In one embodiment the switch (or pair of switches)is a spring switch with a leaf spring contact or button. In anotherembodiment, the switch (or pair of switches) is a micro-switch with aleaf spring lever activation. In yet another embodiment, the switch (orpair of switches) is formed of a conductive strip and a spring loadedconductive strip. One lever arm or and a pair of lever arms of thecharger door of the battery pack charger are used to activate the safetyswitch mechanisms. The one or more lever arms activate (i.e. close, turnON or switch ON) and deactivate the one or more switches (i.e. open,turn OFF or switch OFF) by applying or releasing a pressure or force ona contact point of the leaf spring contact, the button, the leaf springlever, or the spring loaded conductive strip. When the charger door isclosed, the lever arms push on the leaf spring contact, the button, theleaf spring lever, or the spring loaded conductive strip in order toclose the switch to provided a closed circuit. With the charger door inan open position there is no pressure from the lever arm on the leafspring contact, the button, the leaf spring lever, or the spring loadedconductive strip. Therefore, the safety switches are not closed andprovide an open circuit when the charger door is in the open position.When the charger door is in a closed position, the closing of the safetyswitch mechanism (or mechanisms) allows power to be supplied to arechargeable battery pack that is inserted into the battery packcharger.

[0051] The battery pack charger further provides rectangular guide tabson sidewalls of an inner housing that allow the rectangular guide tabsof the rechargeable battery pack to slide under. The rectangular guidetabs of the battery pack charger further distinguish the type ofrechargeable battery packs that can be fully inserted therein for safecharging.

[0052] The battery pack charger further includes a charger power supplyon a printed circuit board with the appropriate circuitry to charge therechargeable battery pack at the at least one fast charge rate. Thebattery pack charger includes a temperature sensor coupled to theprinted circuit board at one end that reaches through the opening in therechargeable battery pack to directly sense battery temperature at aterminal case of a rechargeable battery cell in the rechargeable batterypack.

[0053] Reference is now made to FIGS. 1-11 illustrating the rechargeablebattery pack 100 of the present invention. FIG. 1 is a front perspectiveview from above of a first embodiment of the rechargeable battery pack100. Rechargeable battery pack 100 may also be referred to as a batterypack, energy pack or rechargeable battery cassette. FIG. 2 is a rearperspective view from below the first embodiment of the rechargeablebattery pack 100. The rechargeable battery pack 100 includes a batterypack case 102, a first electrical contact 104 in a right side 106, asecond electrical contact 105 in a left side 107, and one or morerechargeable batteries to store an electrical charge or energy. Therechargeable batteries are housed by the battery pack case 102 and canbe Nickel-Cadmium (NiCad), Nickel-Metal-Hydride (NiMH), lithium-ion orother type of rechargeable battery. The rechargeable battery pack 100 isoften used in children's toys and radio controlled vehicles receivers ortransmitters.

[0054] The rechargeable battery pack case 102 is preferably made of aninexpensive rigid material such as plastic and may also be an insulatingmaterial so as not to short to metal electrical contact points orterminals. The first electrical contact 104 protrudes through an openingin the right side 106 of the battery pack case 102. The secondelectrical contact 105 protrudes through an opening in the left side 107of the battery pack case 102. The first and second electrical contacts,also referred to as terminals, are for making an electrical connectionto terminals of a battery powered device and a battery pack charger.Preferably the first electrical contact 104 on the right side 106 is anegative contact for coupling to the negative terminal of the batterypack charger or battery powered device. The second electrical contact105 on the left side 107 is preferably a positive contact for couplingto the positive terminal of the battery pack charger or battery powereddevice.

[0055] A front side 108 of the battery pack case 102 has an opening 110to allow contact to battery casing of the rechargeable battery 111A by atemperature sensor probe to thermally couple thereto. Opening 110 may berectangularly shaped as illustrated or round, oval or otherwise to allowthe temperature sensor probe to make contact with the rechargeablebattery 111A. The opening 110 exposes the terminal casing of therechargeable battery 111A near its end terminal. The exposed terminalcasing preferably includes conductive material that is electrically andthermally coupled to the end terminal of the battery. In the preferredembodiment, the opening 110 is nearer the right side 106 to expose theterminal casing for the negative terminal of the rechargeable battery111A. The opening 110 allows a battery pack charger that has atemperature sensor to make contact with the rechargeable battery 111A tomeasure its temperature at its terminal casing. In the preferredembodiment, the temperature sensor of a battery pack chargermechanically, thermally and electrically couples to the terminal casingof the rechargeable battery 111A.

[0056] Measuring the temperature of the rechargeable battery 111A canprovide an indication of the charge condition of the battery in order tomake determinations of charge current levels. If the rechargeablebattery 111A is measured to have too high of a temperature, the chargingcan be stopped or reduced to a slow or trickle charge current level. Theopening 111A facilitates one of the safety features of the presentinvention. If the rechargeable battery 111A includes conductive materialconnected to the electrical terminal of the battery as its exposedcasing, the opening 110 allows the temperature sensor of the batterypack charger to make electrical contact with the rechargeable battery111A. The electrical connection provides a means to assure that thetemperature sensor is making proper contact with the rechargeablebattery 111A by operating in a closed circuit. If not in a closedcircuit, an open circuit exist and the battery pack charger may notcharge at the fast charge rates as a result of a defect in thetemperature sensing mechanism. In the preferred embodiment, therechargeable battery 111A has a portion of an insulating skin cut awayto reveal the conductive terminal casing of the negative terminal of therechargeable battery 111A. Referring momentarily to FIG. 11, the area112 of the insulating skin 114 of the rechargeable battery 111A has beencut away to allow direct contact by a temperature sensor to the negativeterminal casing.

[0057] Referring now to FIGS. 1 and 2, a top rear edge 116, where a topsurface 118 and a rear side 120 meet, includes one or more key slots 122which are openings or recesses in the material forming the top rear edge116 of the case. The openings for the key slots 122 extend from the apart of the rear side 120 through a part of the top surface 118 as shownin FIGS. 1 and 2. Referring momentarily to FIGS. 9 and 10, one elongatedkey slot 122′ is illustrated along the top rear edge 116 as an alternateembodiment to the one or more key slots 122. Referring back to FIGS. 1and 2, the one or more key slots 122 provide one of the safety featuresof the present invention. As discussed more fully later, the one or morekey slots 122 act like keys for the rechargeable battery pack 100. Thekey slots 122 can mate to a locking feature in a battery pack charger inorder to assure that a specific rechargeable battery pack is installedin the battery pack charger. The key slots 122 and locking featureprecludes other rechargeable battery packs from being inserted andcharged. This is because other rechargeable battery packs were notspecifically designed to be safely charged by the given battery packcharger.

[0058] Various combinations in number, positions and sizes of the one ormore key slots 122 along the rear edge 116 can be used to distinguishdifferent rechargeable battery packs 100. For example, rechargeablebattery packs may have different rechargeable battery types (i.e.Nickel-Cadmium, Lithium Ion, etc.) or differing numbers of rechargeablebatteries with different voltage and/or current capabilities. The one ormore key slots 122 along the rear edge 116 of the battery pack 100 canbe used to distinguish these differences in the same battery case 102having the same form factor. Additionally the one or more key slots 122can distinguish between battery packs with or without the opening 110.For example, rechargeable battery packs without the opening 110 do notprovide a means for measuring the temperature at near the end terminalof the rechargeable battery 111A. It would therefore be unsafe to fastcharge rechargeable battery packs without the opening 110 in a batterypack charger that fast charges and measures temperature through theopening 110 to determine when to slow or trickle charge. In which casethe battery pack charger may continue to fast charge and may causedamage to the rechargeable battery pack, the battery pack charger orother property or persons. It is therefore desirable to differentiatebetween rechargeable battery packs that have the opening 110 from thosethat do not. The one or more key slots 122 can also provide a means ofdifferentiating or distinguishing those rechargeable battery packs thathave the opening 110. As an additional safety feature, the battery packcharger can detect when an electrical contact is made between thetemperature probe and the terminal case of a rechargeable battery pack.Therefore, if the opening 110 in the case of the battery pack ismissing, the temperature probe does not make contact and charging at afast charge rate can be avoided or charging can be completely turned OFFin response.

[0059] The battery pack case 102 of the rechargeable battery pack 100 isrectangularly shaped. The size of the rechargeable battery pack case 102in one embodiment is the same as the other rechargeable battery packs,such as the typical, in order to be backward compatible. That is, therechargeable battery pack 100 has the same size and same location ofelectrical contacts so that it can be used to power former batterypowered devices and be charged in former battery pack chargers. Inanother embodiment, the size, shape and location of electrical contactsof the rechargeable battery pack are proprietary and incompatible whencompared with former rechargeable battery packs. In either case, theopening 110 and the key slots 122 provide safety features to assure theproper charging with the appropriate battery pack charger at fast chargerates. Additionally, the rechargeable battery pack 100 may be flexiblesuch as that disclosed in U.S. Pat. No. 5,853,915 entitled “FoldableMulti-configuration Battery Pack” by Shohei Suto and incorporate theopening 110 at a front side and the one or more key slots 122 at an edgesuch as the rear edge.

[0060] In the preferred embodiment, the rechargeable battery pack case102 includes rectangular guide tabs 124A and 124B along base regions126A and 126B on the right side 106 and left side 107 respectively. Inthe embodiment where the rechargeable battery pack is backwardcompatible with former battery powered devices, there are two L shapedtabs 128 and 129 along the base region 126A on the right side 106 andtwo mirrored-L shaped tabs 130 and 131 along the base region 126B of theleft side 107. The rectangular guide tabs 124A and 124B are the firstguide tabs upon insertion and are nearest the front side 108 onrespective right and left sides of the rechargeable battery pack. Thetabs 128 and 130 are nearest the middle on respective right and leftsides between the front side 108 and the rear side 120. The tabs 129 and131 are the last guide tabs nearest the rear side 120 on respectiveright and left sides of the rechargeable battery pack. The twomirrored-L shaped tabs 130 and 131 on the left side are essentially themirror images of the two L shaped tabs 128 and 129 on the right side. Inanother embodiment the tabs 128-131 are shaped to match a proprietarybattery powered device. The rectangular guide tabs 124A and 124B and thetwo L shaped tabs 128-129 and the two mirrored-L shaped tabs 130-131protrude from the narrower base regions 126A-126B to approximately havethe same width of the rechargeable battery pack 100. Each of therectangular guide tabs 124A and 124B include a front side, a rear sideopposite the front side, a bottom side, a top side opposite the bottomside, and a front edge where the front side and bottom side couple. Eachof the L shaped guide tabs 128-129 and mirrored-L shaped guide tabs130-131 include horizontal portions referred to as feet and verticalportions. The guide tabs 124A and 124B, tabs 128-129, and shaped tabs130-131, whatever their shape, guide and hold the rechargeable batterypack 100 in contact to the terminals of a battery powered device whenproperly engaged therein. The rectangular guide tabs 124A and 124B, Lshaped guide tabs 128-129, and mirrored-L shaped guide tabs 130-131,also provide a quick-load system and reverse polarity protection in thatthey protect the rechargeable battery pack 100 from being insertedimproperly into a battery charger.

[0061] In order to inform a user of the insertion direction of therechargeable battery pack 100 into a battery pack charger, an arrow 132may be included in or on the top surface 118 as illustrated in FIG. 1.In order to further identify the rechargeable battery pack 100 with theproper battery pack charger, colored labels 134 and 136 may be includedin the top surface 118 and a bottom surface 138 respectively matchingthe color of a color label affixed to the battery pack charger (notshown). A user need only match the color of the label of therechargeable battery pack with the color of the label on the batterypack charger to know that it can properly be charged therein.

[0062] Referring now to FIG. 9, a rear elevational view of a secondembodiment of the rechargeable battery pack 100 is illustrated. Thesecond embodiment of the rechargeable battery pack 100 includes theelongated key slot 122′ along the top rear edge 116. Referring to FIGS.9 and 10, the elongated key slot 122′ is an opening or recess in thecase 102 of the rechargeable battery pack 100 that extends from the rearside 120 to the top surface 118 along the top rear edge 116. Asdescribed in more detail below, the elongated key slot 122′ mates with asurface of the battery pack charger to mechanically distinguish it fromother types of rechargeable battery packs.

[0063] Referring now to FIG. 11, a front perspective exploded view fromthe top of the rechargeable battery pack 100 of the present invention isillustrated. The rechargeable battery pack 100 includes a plurality ofrechargeable batteries 111A-111E connected in series together to formthe desired voltage level of the rechargeable battery pack 100.Rechargeable batteries 111A-111E are preferably nickel-cadmiumbatteries, but, they also may be lithium-ion, nickel metal hydride orother rechargeable type of battery. FIG. 11 illustrates only fourbatteries connected in series but it is to be understood that more orless can be connected in series without departing from the spirit of thepresent invention. To couple the rechargeable batteries 111A-111E inseries a number of shorting strips 140 can be used coupling the negativeterminal of one rechargeable battery to the positive terminal of anotherrechargeable battery. Shorting strips 140 are conductive strips that arepreferably metallic. The first electrical contact 104 of therechargeable battery pack 100 is coupled to one end of wire 148B whilean opposite end of wire 148B is coupled to the end terminal 142 of therechargeable battery 111A. In this manner, the first electrical contact104 couples to the end terminal 142 of the rechargeable battery 111A. Inthe preferred embodiment, the end terminal 142 is the negative terminal.An end terminal 144 of the rechargeable battery 111E is coupled to oneside of a metal contact 146. The second side of the metal contact 146 iscoupled to one end of wire 148A. The opposite end of wire 148A iscoupled to the second electrical contact 105 of the rechargeable batterypack 100. In this manner, the second electrical contact 105 couples tothe end terminal 144 of the rechargeable battery 111E. In the preferredembodiment, the end terminal 144 is the positive terminal.

[0064] After coupling the rechargeable batteries 111A-111E in series andto the contacts, they can be fitted into a bottom half 150 of thebattery pack case 102. Then a top half 152 of the battery pack case 102can be fitted over the rechargeable batteries 111A-111E, contacts, andshorting bars to enclose them and hold them in place. The top half 152includes a right side contact opening 154 and a left side contactopening 155 to allow the first and second electrical contacts 104 and105 respectively to protrude through the battery pack case 102. The area112 of the insulating skin 114 of the rechargeable battery 111A has beencut away to allow direct contact to the terminal casing of therechargeable battery 111A. In the preferred embodiment it is thenegative terminal casing that is exposed through the area 112. Area 112may be a small rectangular area as illustrated or it may be acylindrical region around the battery 111A or a circular area or othershaped area that allows a temperature sensor to make direct contact toexposed terminal casing therein.

[0065] In order to allow a temperature sensor to reach in through to therechargeable battery 111A, the battery pack case 102 includes theopening 110. The opening 110 may be completely formed in the top half152 of the battery pack case 102. Alternatively, a portion of opening110 can be formed in the top half 152 and another portion of opening 110can be formed in the bottom half 150 of the battery pack case asillustrated in FIG. 11.

[0066] To complete the construction of the rechargeable battery pack 100in its partial assembled form, the top half 152 is fixed to the bottomhalf 150 by either a glue, adhesive or an epoxy or by thermally fusingthe materials together such as through welding. The top half 152 canvary depending upon the configuration of the one or more slots 122 thatare used to distinguish the rechargeable battery pack 100. Base regions126A and 126B are recesses in the right side 106 and left side 107respectively of the bottom half 150 of the battery pack case 102.

[0067] As illustrated in FIG. 11, base region 126A includes therectangular guide tab 124A, the L shaped tab 128, and the L shaped tab129 protruding there from. The backward compatibility provided by therectangular guide tabs 124A-124B, the L shaped tabs 128-129 andmirrored-L shaped tabs 130-131 allow the rechargeable battery pack 100to be inserted into former battery pack chargers that charge at a slowcharge rate. The backward compatibility provided by the rectangularguide tabs 124A-124B, the L shaped tabs 128-129 and mirrored-L shapedtabs 130-131 also allow the rechargeable battery pack 100 to be insertedinto former battery powered devices.

[0068] Referring now to FIG. 12, a battery pack charger 200 of thepresent invention is illustrated. Battery pack charger 200 includes apair of AC power spades 201 integrated into the battery pack charger 200so it can directly couple into an AC outlet 302 without the use of anelectrical cord. Battery pack charger includes a charger case 202 thatincludes a top half case 204 and a bottom half case 206. The top halfcase 204 includes air slot openings 208A-208C as illustrated in FIGS. 12and 13 to allow airflow around the electronic components containedtherein.

[0069] Referring now to FIG. 13, a perspective view of the battery packcharging system of the present invention is illustrated. The batterypack charging system of the present invention includes the battery packcharger 200 and the rechargeable battery pack 100. The battery packcharger 200 can charge at a trickle charge rate and at least one fastcharge rate to speed charging of the rechargeable battery pack 100. Themechanical safety precautions provided by the present invention areundertaken in order to provide a safe battery pack charging system thatcan safely charge at the at least one fast charge rate.

[0070] The battery pack charger 200 includes a charger door 210 whichopens and closes over an opening 212 within the battery pack charger200. The rechargeable battery pack 100 is inserted into and extractedfrom the battery pack charger 200 through the opening 212. The chargerdoor 210 at its exterior includes a knob 214 protruding from a rearsurface, a left side arc shaped lever arm 215 protruding from a leftside surface, and a right side arc shaped lever arm 216 protruding froma right side surface. The left side arc shaped lever arm 215 and rightside arc shaped lever arm 216 move through slots 217 and 218respectively in the top half case 204. The left side arc shaped leverarm 215 and right side arc shaped lever arm 216 allow the charger door210 to rotably open in an arc to allow access to the opening 212. At endof each arc shaped lever arm 215-216 is a protrusion (not shown in FIG.13, see FIG. 14) forming a latch 219 that latches to the top half case204 when the charger door 210 is closed. Additionally, the end of eacharc shaped lever arm 215-216 is shaped to form a leaf spring mechanicalcontact point. At an interior of the charger door 210 there are tworectangular latches 220 protruding from the rear edge that mate to tworectangular recesses 222 in the top half case 204 to further hold thecharger door 210 in a closed position. The knob 214 allows a user toopen and close the charger door 210. The battery pack charger 200further includes a catch mechanism 224 that has left and right sidefinger releases 225-226 protruding through openings at the edge of thebottom half case 206 and top half case 204. The catch mechanism 224described in more detail below is to lock the rechargeable battery pack100 in place within the battery pack charger 200 so it doesn't fall orspring out of opening 212. The battery pack charger 200 further includeslight emitting diode (LED) lenses 228 made from clear plastic to magnifythe light intensity of LED's that may glow underneath.

[0071] Referring now to FIG. 14, a left side view of the battery packcharger 200 with the top half case 204 separated is illustrated. Theright side is substantially a mirror image of the left side. The batterypack charger 200 further includes a charger power supply (e.g. anon-isolated switching power supply or a linear power supply) on aprinted circuit board (PCB) 232 having an electronic control system. Thecharger power supply includes a bridge network to couple through thesafety switch mechanisms and the AC power spades 201 to receive an ACline voltage and a non-isolated flyback transformer 230. The chargerpower supply generates a relatively low DC voltage having at least onehigh current rate which is used for the fast charge current and supplyvoltage of the charging output power. An electronic control system onthe printed circuit board 232 couples to the charger power supply tocontrol the charge current output including a trickle charge rate andthe at least one fast charge rate. The electronic control system of thePCB 232 preferably senses temperature remotely, through signals from atemperature sensor, at the rechargeable battery 111A of the rechargeablebattery pack 100 in order to safely control charging at the at least onefast charge rate. The temperature sensor and its connection to theelectronic control system are discussed more below with reference toFIG. 18.

[0072] To assure that a charge voltage and current is safely applied,the battery pack charger includes one or a pair of safety switchmechanisms. In one embodiment, the pair of safety switch mechanisms areformed from a first pair of leaf spring conductive strips 234A-234B eachhaving a leaf spring contact 235A-235B at one end and an electricalcontact 236A-236B at another end, a pair of stationary contact strips239A-239B, and the left and right side arc shaped lever arms 215-216 ofthe charger door 210. A pair of spring loaded strips 240A-240B areisolated from the stationary contact strips 239A-239B. In FIG. 14 onlythe left side is shown illustrating the leaf spring conductive strip234A and the stationary contact strip 239A. Referring momentary to FIG.17, the stationary contact strip 239A is on the left side and thestationary contact strip 239B is on the right side when viewed fromabove. The leaf spring conductive strip 234B and the stationary contactstrip 239B and their respective elements on the right side are a mirrorimage of those on the left side and therefore need no furtherillustration.

[0073] Referring back to FIG. 14, each electrical contact 236A-236B ofthe respective leaf spring conductive strips 234A-234B and eachstationary contact strip 239A-239B electrically couple between the ACline and the input terminals of the power supply of the printed circuitboard 232. A screw on each side adjustably couples an end of each leafspring conductive strip 234A-234B to an inner surface of the batterypack charger 200. Each leaf spring conductive strip 234A-234B is arcshaped near each leaf spring contact 235A-235B to form the leaf spring.Each leaf spring conductive strip 234A-234B is preferably formed of ametal strip such as copper in order to conduct electricity and form aleaf spring.

[0074] Each stationary contact strip 239A-239B is preferably formed of ametal strip such as copper in order to conduct electricity. Eachstationary contact strip 239A-239B has an L shaped bracket formed nearits end with an opening at its foot to allow a screw to be inserted andaffix each to the battery pack charger 200. Each stationary contactstrip 239A-239B is held in a stationary position inside the battery packcharger 200 in order to couple to the leaf spring conductive strips234A-234B.

[0075] The spring loaded contact strips 238A-238B are for coupling tothe terminals of a rechargeable battery pack 100 and are preferablyformed of a metal strip such as copper in order to conduct electricity.Each of the spring loaded contact strips 238A-238B are electricallyisolated from the stationary contact strips 239A-239B respectively. Eachof the spring loaded contact strips 238A-238B has a spring loadedconductive strip portion 240A-240B which is U-shaped. The U-shapedspring loaded conductive strip portions 240A-240B extend throughopenings in the inner housing of the battery pack charger 100, preparedto make contact with contact terminals of a rechargeable battery pack100. The base of the U-shaped spring loaded conductive strip portions240A-240B extending through openings of an inner housing make contactwith the first and second electrical contacts 104-105 when arechargeable battery pack 100 is completely inserted into opening 212.Because the U-shaped spring loaded conductive strip portions 240A-240Bextend through openings of the inner housing 250, the spring loadedcontact strips 238A-238B may be touched by a user through opening 212when the charger door 210 is open. The leaf spring conductive strips234A-234B and each stationary contact strip 239A-239B, coupling to theAC line voltages, are behind the walls of the inner housing 250 withoutan opening or extension into the inner housing 250 and therefore can notbe touched by a user.

[0076] In order to avoid shocking a user who may touch electricalcontacts, such as a child, it is desirable to avoid placing a voltageonto the spring loaded contact strips 238A-238B while the charger door210 is open. FIG. 19 illustrates the charger door 210 in an openedposition while FIG. 20 illustrates the charger door 210 in a closedposition. To automatically avoid a user from getting shocked, the safetyswitch mechanisms are employed. Each leaf spring conductive strip234A-234B and each stationary contact strip 239A-239B is mounted in thebattery pack charger such that there is a gap 241A between the leafspring contact 235A and the stationary contact strip 239A and a gap 241Bbetween the leaf spring contact 235B and the stationary contact strip239B, when the charger door 210 is in an open position. The gaps241A-241B between the contacts of the conductive strips electricallydecouple each stationary contact strip 239A-239B from each leaf springconductive strip 234A-234B.

[0077] To close the gap 241A between the leaf spring contact 235A andthe stationary contact strip 239A and the gap 241B between the leafspring contact 235B and the stationary contact strip 239B, therespective end 242A-242B of the left and right side arc shaped leverarms 215-216 of charger door 210 mechanically couple to the backside ofeach leaf spring conductive strip 234A-234B near each leaf springcontact 235A-235B. When the charger door 210 is closed, such asillustrated in FIG. 20, each end 242A-242B of each arc shaped lever arm215-216 sufficiently depresses the leaf spring in each conductive strip234A-234B to close the respective gaps and allow leaf spring contact235A to make contact with the stationary contact strip 239A and the leafspring contact 235B to make contact with the stationary contact strip239B, mechanically and electrically coupling them together.

[0078] The leaf spring switch mechanism opens and closes operationallyby respectively opening and closing the charger door 210 as illustratedby FIGS. 19 and 20. Only when the charger door 210 is closed are AC linevoltages used to provide a charging power to the spring contactterminals 240A-240B through operation of the safety switches. When arechargeable battery pack 100 is inserted into the battery pack charger200, the safety switch mechanisms in one embodiment control when ACpower is coupled into the charger.

[0079] To distinguish rechargeable battery packs that are safe to chargeor otherwise, the battery pack charger in one embodiment includes one ormore key tabs to mate or interface with one or more key slots of therechargeable battery pack. The one or more key tabs may be positionedinside the inner housing, such as at the front surface, of the batterypack charger or coupled to a charger door. In this case the rechargeablebattery pack needs to have the one or more key slots properly positionedto mate so that so that the charger door can close or so that it can befully inserted into the housing and the charger door can close. Inanother embodiment, the key slots and key tabs are swapped such that thebattery pack charger has the one or more key slots and the rechargeablebattery pack has the one or more key tabs. The one or more key slots maybe positioned inside the inner housing, such as at the front surface, ofthe battery pack charger or in the charger door. In this case, therechargeable battery pack needs to have the one or more key tabsproperly positioned to mate with the one or more key slots in thebattery pack charger so that the charger door can close or so that whenfully inserted into the housing the rechargeable battery pack causes asafety switch to close and the rechargeable battery pack can be charged.

[0080] Referring now to FIG. 15, a bottom sectional view from the rearof a first embodiment of charger door 210 is illustrated. The chargerdoor 210 includes the rectangular latches 220 protruding from the bottomedge. The rectangular latches 220 also protrude from a back surface 244of the charger door as illustrated. The first embodiment of charger door210 further includes one or more key tabs 246 that protrude from theback surface 244 and a bottom surface 248. The one or more key tabs 246mate with the one or more key slots 122 of the first embodiment of therechargeable battery pack 100 when the charger door 210 is closed. Ifthe pattern of the one or more key slots 122 on a rechargeable batterypack differs in number or position from those of the one or more keytabs 246, charger door 210 will not close completely to operationallyclose the leaf spring switch mechanism and complete a circuit. In thiscase, the rechargeable battery back with the differing one or more keyslots 122 will not be charged. The one or more key tabs 246 providedifferentiation between the types of rechargeable battery packs that canbe charged within the battery pack charger 200. One point ofdifferentiation is whether a rechargeable battery pack has opening 110or not to allow a temperature sensor to probe the battery temperature.The one or more key tabs 246 and the one or more key slots 122, providesassurance that the proper type of rechargeable battery pack 100 will besafely charged within the battery pack charger 200 for which it wasdesigned.

[0081] Referring now to FIG. 16, a bottom sectional view from the rearof a second embodiment of charger door 210 is illustrated. The secondembodiment of charger door 210 includes an elongated key tab 246′ thatprotrudes from the back surface 244 and the bottom surface 248. Theelongated key tab 246′ mates with the elongated key slot 122′ of thesecond embodiment of the rechargeable battery pack 100 when the chargerdoor 210 is closed. If the size of the elongated key slot 122′ on arechargeable battery pack differs in size or position from those of theelongated key tab 246′, charger door 210 will not close completely tooperationally close the leaf spring switch mechanism and complete acircuit. In this case, the rechargeable battery back with the differingelongated key slot will not be charged. The elongated key tab 246′provides differentiation between the types of rechargeable battery packsthat can be charged within the battery pack charger 200. One point ofdifferentiation that the charger door 210 can provide is whether or nota rechargeable battery pack has opening 110 to allow a temperaturesensor to probe the battery temperature while fast charging.

[0082] Referring now to FIG. 17, a top sectional view of the bottom halfcase 206 of the battery pack charger 200 without the printed circuitboard 232 and transformers s illustrated. FIG. 17 illustrates thestationary contact strips 239A and 239B and how they are held in astationary position inside the battery pack charger 200. FIG. 17 furthershows the spring loaded contact strips 238A-238B with their U-shapedspring loaded strip portions 240A-240B extending through openings of theinner housing 250. Details of the catch mechanism 224 are also visiblein FIG. 17. The catch mechanism 224 includes the finger releases 225 and226 that protrude through the charger case 202. The catch mechanism 224also includes a spring lever arm 252 near its mid point, a left catch253 and a right catch 254 at opposing ends of a pair of catch arms. Thepair of catch arms and the spring lever arm are coupled to a pivot shaftthat allows them to rotate in an arc providing an up and down movement.The finger releases 225 and 226 are coupled to center portions of thepair of catch arms. Underneath the spring lever arm 252 is a spring 256to lift up the left catch 253 and right catch 254 so as to protrude thebottom of the inner housing 250. The left catch 253 and the right catch254 engage the rear sides of the respective rectangular guide tab124A-124B of the rechargeable battery pack 100 to hold it in place. Theleft catch 253 and right catch 254 are each ramped shaped from a rearedge toward their tops to slidably engage the rechargeable battery pack100 when its inserted. Initially the front edges and then the bottomsides of the rectangular guide tabs 124A-124B of the rechargeablebattery pack 100 slidably engage the ramps of the right catch 254 andthe left catch 253 to depress the catch mechanism 224 and compress thespring 256. The front sides of the left catch 253 and the right catch252, being furthest from the lever arm 252, are vertical surfaces. Thisis so that the rectangular guide tabs 124A-124B, after completelypassing over the left catch 253 and the right catch 254, can be lockablyengaged and not slidably depress the catch mechanism in the reversedirection. When a user presses either or both finger releases 225 and226, the spring 256 compresses and the catches 253-254 are depressedbelow the bottom of the inner housing 250 to allow the rectangular guidetabs 124A-124B and the rechargeable battery pack 100 to slide out fromthe opening 212.

[0083] Coupled to the side walls of the inner housing 250 are a leftrectangular guide tab 257 and a right rectangular guide tab 258. Uponinsertion of rechargeable battery pack 100, the rectangular guide tabs124B and 124A of the rechargeable battery pack 100 slide under the leftrectangular guide tab 257 and the right rectangular guide tab 258respectively when initially slid in. The rectangular guide tabs124A-124B then slide over the respective catches 253-254 to depress themand compress the spring 256 momentarily until the rear sides of therectangular guide tabs 124A-124B clear. After the catches 253-254 havecleared the rear sides of the rectangular guide tabs, the spring 256decompresses and lifts the left catch 253 and right catch 254 toprotrude through the bottom of the inner housing 250 behind them to holdthe rechargeable battery pack in place. Feet of the mirrored-L shapedtab 130 and the L shaped tab 128 first slide under the left rectangularguide tab 257 and the right rectangular guide tab 258. A rear portion ofeach of the left rectangular guide tab 257 and the right rectangularguide tab 258 then engage respectively with the mirrored-L shaped tab130 and the L shaped tab 128. The rechargeable battery pack 100 slidesinto opening 212 until the vertical portions of the mirrored-L shapedtab 130 and the L shaped tab 128 catch the respective rear portions ofthe left rectangular guide tab 257 and the right rectangular guide tab258 to stop it.

[0084] The left rectangular guide tab 257 and the right rectangularguide tab 258 provide a further safety feature in that they stop formerrechargeable battery packs from being completely inserted and unsafelycharged therein. Former rechargeable battery packs first have an Lshaped tab and an mirrored-L shaped tab on respective sides in frontnearest the terminals which keep it from being completely inserted intothe battery pack charger 200. The vertical portion of the firstmirrored-L shaped tab and the first L shaped tab of the formerrechargeable battery packs catch the rear portions of the leftrectangular guide tab 257 and the right rectangular guide tab 258 tostop it from further insertion. Thus, the left rectangular guide tab 257and the right rectangular guide tab 258 act as deterrents to insertingformer rechargeable battery packs, not having opening 110 fortemperature sensing, into the fast charging system of the presentinvention with the at least one fast charging rate. The battery packcharger essentially has features to lock out rechargeable battery packsthat are unsafe to charge at its at least one fast charge rate. To makean electrical coupling to the rechargeable battery pack 100, theU-shaped conductive strip portions 240A-240B extend through openings ofthe inner housing 250 become compressed and couple to the secondelectrical contact 105 and the first electrical contact 104 respectivelyupon full insertion of the rechargeable battery pack 100. Thetemperature sensor contact 259 protrudes out through an opening and intothe inner housing 250 to make contact with an inserted rechargeablebattery through its opening 110.

[0085] Referring now to FIG. 18, a magnified sectional view of thetemperature sensor area of the battery pack charger 200 and rechargeablebattery pack 100 is illustrated. The battery pack charger 200 includes atemperature sensor for sensing battery temperature. The temperaturesensor, also referred to as a temperature probe herein, is used todetermine the optimum time to turn off at least one fast charge rategenerated by the battery pack charger 200. In the preferred embodiment,the temperature sensor is a thermistor 260 coupled to the temperaturesensor contact 259 as shown in FIG. 18. A thermistor is an electronicdevice that makes use of a change in the resistivity of a semiconductorto indicate change in temperature. The resistance of a thermistor variesas a function of temperature when heat is applied. Other electronicdevices that can measure or sense temperature and vary resistance,current or voltage of the electronic device as a function oftemperature, may be substituted for a thermistor.

[0086] The thermistor 260 is electrically coupled to the electroniccontrol system of the printed circuit board 232 through wire 262 at oneend. The thermistor 260 protrudes through the inner housing 250 and ismechanically and electrically coupled to the contact terminal 259.Preferably the thermistor 260 is soldered to the contact terminal 259.The contact terminal 259 protrudes from the inner housing 250 throughthe opening 110 in the rechargeable battery pack 100 to make contactwith the rechargeable battery 111A. The thermistor 260 couples throughthe contact terminal 259 to the terminal case of the rechargeablebattery 111A in the area 112 where the insulating skin 114 is removed.

[0087] Heat at the terminal case in the area 112 of the rechargeablebattery 111A is conducted into the front side of temperature sensorcontact 259 through to its back side and into the thermistor electrodeof the thermistor 260 coupled to the backside of the temperature sensorcontact 259. Heat at the thermistor electrode conducts into the body ofthe thermistor 260 and causes its resistance to vary indicating ameasure of battery temperature. The heat conducting materials betweenthe battery 111A and the thermistor 260 are preferably metallic in orderto better conduct heat.

[0088] The thermistor 260, coupling to the conductive terminal casing ofthe rechargeable battery 111A, completes a circuit through therechargeable battery casing, the spring loaded contact strip 238B, andthe leaf spring conductive strip 234B to the electronic control systemof printed circuit board 232. In this manner the thermistor and thethermistor circuit can be analyzed to determine if its functioningproperly.

[0089] Referring now to FIGS. 19 and FIG. 20. FIG. 19 illustrates aright side cut-away sectional view of the battery pack charger 200 withits charger door 210 open ready to receive the rechargeable battery pack100. To keep the charger door 210 open to insert a rechargeable batterypack 100, a pair of springs 233 are used each coupling to an end of thelever arms 215-216 and a pair of tabs one each side of the bottom halfcase 206. FIG. 20 illustrates a right side cut-away sectional view ofthe battery pack charger 200 with the rechargeable battery pack 100completely engaged therein with its charger door 210 closed. The sideview of the charger door 210 and rechargeable battery pack 100illustrates how the one or more key tabs 246 mate with the one or morekey slots 122 of the rechargeable battery pack 100 when its inserted.

[0090]FIG. 19 illustrates how the rechargeable battery pack 100 engagesthe left catch 253 and the rectangular guide tab 124B in greater detailwith the right catch 254 and rectangular guide tab 124A being mirrorimages. The left catch 253 has a ramp shaped on the rear side and avertical surface on the front side so that the rectangular guide tab124B of the rechargeable battery pack can depress it when inserted butnot after it has passed. The placement height on the sidewall of therectangular guide tab 252 from the bottom of the of the inner housing250, allows the rectangular guide tab 124B to slide underneath.

[0091] As illustrated in FIG. 19 with the charger door 210 being open,there is a gap 241A between the leaf spring contact 235A of the leafspring conductive strip 234A and the stationary contact 239A of thespring loaded conductive strip 239A. When closing the charger door 210,the arc shaped lever arm 215 rotates through an arc so that the end 242Amechanically couples to the leaf spring conductive strip 234A near theleaf spring contact 235A. Closing the charger door 210 further to itsclosed position compresses the leaf spring of the leaf spring conductivestrip 234A sufficiently enough such that the leaf spring contact 235Acontacts the stationary contact 239A electrically coupling them togetherwhile the charger door 210 is closed.

[0092]FIG. 20 illustrates how the rectangular latches 220 on chargerdoor 210 interface to the rectangular recesses 222 when it is fullyclosed. The rectangular latches 220 engaged into the rectangularrecesses 222 keep the charger door 210 closed and do not allow thespring force of the leaf spring conductive strips 234A-234B to force itopen.

[0093] To extract the rechargeable battery pack 100 from the batterypack charger, a user opens the charger door 210 using knob 214 todisengage the rectangular latches 220 from the rectangular recesses 222.The user then presses down on one or both of the finger releases 225-226moving the catch mechanism to compress the spring 256 and lower its armsand the left and right catches 253-254. With the charger door 210 openand the catch mechanism depressed, the rear of the rechargeable batterypack can be grabbed by a user and pulled out.

[0094] Referring now to FIGS. 21, 22 and 23, an alternate embodiment ofthe battery pack charger 200′ is illustrated. In this alternateembodiment, the safety switch mechanisms are implemented usingmicro-switches 334A and 3343. Micro-switches 334A and 334B and springloaded conductive strips 338A and 338B in FIGS. 21, 22, and 23 havereplaced the leaf spring conductive strips 234A and 234B, leaf springcontacts 235A and 235B, electrical contacts 236A and 236B, stationarycontacts 239A and 239B, and gaps 241A and 241B in FIGS. 14, 17, 19, 20.Otherwise, the battery pack charger 200′ is similar to the battery packcharger 200.

[0095] Referring now to FIG. 21, a right side cut-away sectional view isillustrated of the alternate embodiment of the battery pack charger 200′with its charger door 210 open to receive the rechargeable battery pack100. FIG. 21 illustrates a side view of the micro-switch 334A whilemicro-switch 334B is a mirror image on the opposite side. Micro-switches334A and 334B include spring loaded levers 335A and 335B respectively toactivate (i.e. close or switch ON) and deactivate (i.e. open or switchOFF) them. The spring loaded levers 335A and 335B are electricallyisolated from any switch contacts and thus may be touched by a userwithout risk of shock. The charger door 210 in a closed positionactivates the micro-switches 334A and 334B. The charger door 210 in anopen position deactivates the micro-switches 334A and 334B. The ends242A and 242B of the lever arms 215 and 216 of the charger door 210couple to the spring loaded levers 335A and 335B respectively toactivate and deactivate the micro-switches 334A and 334B. In FIG. 21,the charger door 210 is open and the micro-switches 334A and 334B areboth deactivated.

[0096] Referring now to FIG. 22, a right side cut-away sectional view isillustrated of the alternate embodiment of the battery pack charger 200′with the rechargeable battery pack 100 inserted therein. In FIG. 22, thecharger door 210 is closed so that the micro-switches 334A and 334B areboth activated. The ends 242A and 242B of the lever arms 215 and 216 ofthe charger door 210 apply pressure to the spring loaded levers 335A and335B respectively to activate the micro-switches 334A and 334B.

[0097] Referring now to FIG. 23, a top sectional view is illustrated ofthe alternate embodiment of the battery pack charger 200′. In FIG. 23, atop view of the micro-switches 334A and 334B and spring loaded contactstrips 238A and 238B is illustrated.

[0098] Referring now to FIG. 24, a simplified schematic block diagramrepresentation of the electronics of the battery pack charger 200/200′and battery pack 100/100′ is illustrated. The electronics of batterypack charger operate using a floating ground system based on the AC linepower that is provided. As coupled together in FIG. 24, the electronicsof the battery pack charger 200/200′ includes a fuse F1, a linecapacitor C1, a line filter L1, a first safety switch S1, a secondsafety switch S2, a bridge rectifier (consisting of diodes D1, D2, D3and D4 and resistor R1), a capacitor C2, a power supply 2402, a chargingcontrol 2404, a capacitive reactive power supply 2406, a firstelectrical contact EC1, a second electrical contact EC2, a current senseresistor R2, and a temperature measuring sensor THM with a thermalcontact TM. In the preferred embodiment, the power supply 2402 is aswitching power supply but can be a linear power supply as well togenerate the desired charging power output for the charging voltages andcharging currents. The battery pack charger 200 plugs into an AC linevoltage source through the AC power spades J1 and J2. In the preferredembodiment with switches S1 and S2, either of AC spade J1 or AC spade J2can couple to the hot line voltage or the neutral line voltage. If it isdesirable to use only one safety switch, AC spade J1 and J2 should bepolarized so the hot 120 volt AC line is switched by the one safetyswitch. An AC voltage of approximately 120 volts in the United States(other AC voltages are available in other countries) is found betweennodes L1 and L2 when the AC power spades 201 of the battery pack charger200 are plugged into an AC power outlet such as those found in homes.With the switches S1 and S2 closed, the AC voltage is coupled into thebridge rectifier formed from diodes D1-D4 and resistor R1. The anodes ofdiodes D3 and D4 are coupled together to form a floating ground (FG).The bridge rectifier and capacitor C2 generate a relatively stable DCvoltage between the output BO and floating ground FG. As compared withearth ground, BO and FG are half wave rectified with respect to line ACvoltage and will therefore have one half of the line voltage present oneach point (approximately 60 volts AC). The electrical contact EC2couples to FG through the resistance of resistor R2. The electricalcontact EC1 couples to FG through the impedance of the power supply2402. Because each of these paths are of low impedance, the electricalcontacts EC1 and EC2 and the battery terminals BT1 and BT2 respectivelywill also be at 60 volts AC with respect to earth ground when therechargeable battery pack RB is inserted and switches Sl and S2 areclosed.

[0099] The bridge diode circuit, consisting of diodes D1, D2, D3, and D4and resistor R1, converts the AC line voltage between nodes L1 and L2into a DC voltage which is coupled into the power supply 2402. The powersupply 2402 receives the DC voltage between the output BO and thefloating ground to generate the charging power output on the node CPO.The node CPO from the power supply 2402 is directly coupled to the firstelectrical contact EC1. The charging power output on node CPO from thepower supply 2402 is controlled by the charging controller 2404. Thecharging controller generates a fast/slow charge (FSC) control signalwhich is coupled into the power supply 2402. The FSC control signalselects the charging power output CPO from the power supply 2402 inresponse to electrical conditions surrounding the terminals that cancouple to a rechargeable battery pack 100. The charging controller 2404receives the charge voltage from the power supply 2402 on CPO, anindicator of battery temperature on TS, and an indication of the currentsupply IS through a rechargeable battery pack. A temperature sensor THM(such as a thermistor) is used to provide an indication of batterytemperature through its proportionate variable resistance overtemperature. The temperature sensor THM can provide an indication of thetemperature of a rechargeable battery in the rechargeable battery pack100 to help determine the overall charge condition of the rechargeablebattery pack. The temperature indication of the rechargeable batteryprovides an indication of the charge condition of the rechargeablebattery pack 100. The temperature indication from the temperature sensorTHM is coupled into the charging controller 2404 on TS. The currentsupply IS is sensed by measuring the voltage across the resistor R2 fromthe second electrical contact EC2. R2 is a known low value and dependingupon the voltage level, the current level can be determined from theequation for Ohm's Law where current equals the measured voltage dividedby the resistance (I=V/R).

[0100] While the power supply 2402 generates the high power supply forcharging rechargeable battery packs, the capacitance reactive powersupply 2406 generates a circuit power CP for the charging control logic2404. The circuit power CP is a stable low power supply so that thecharging control logic 2404 accurately generates control signals forcontrolling the power supply 2402 and the charging of a rechargeablebattery pack 100.

[0101] The power supply 2402, charging control 2404, capacitive reactivepower supply 2406, and resistor R2, all have their respective circuitgrounds coupled to the floating ground FG. Because FG can float to onehalf line voltage or more in the US and is coupled into these circuits,the electrical contacts EC1 and EC2 and the thermal contact TM can alsofloat to such AC levels. If a user were to touch any of these threecontacts, a shock could result if the user were simultaneously touchingan earth ground source.

[0102] Additionally, the power supply 2402 includes a non-isolatedtransformer in the switching power supply embodiment to generate a DCpower output for the charging currents and charging voltages. Anon-isolated transformer is desirable because of its desired performancecharacteristics, its small size and its low cost. However, anon-isolated transformer allows line voltages to be coupled to thecircuitry and can therefore couple a high voltage into the first contactterminal EC1 when compared to earth ground. Furthermore, resistor R2 iscoupled on one end to the floating ground FG and another end to thesecond electrical contact EC2. As a result, floating ground FG cancouple a high voltage into the second contact terminal when compared toearth ground.

[0103] Because the voltage potential on electrical contacts EC1 and EC2may be high when compared to earth ground, it is desirable to protect auser from touching either. The safety switches S1 and S2 provide themeasure of safety by opening a circuit when switched opened (i.e.deactivated, turned off or switched off) and closing a circuit whenswitched closed (i.e. activated, turned on or switched on). In FIG. 24,safety switch S1 essentially opens and closes the circuit between ACspade J1 and its path to floating ground FG. In FIG. 24, safety switchS2 essentially opens and closes the circuit between AC spade J2 and itspath to floating ground FG. The opening and closing of switches S1and/or S2 and their respective circuits, causes the power supply 2402and the capacitive reactive power supply 2404 and other circuitry topower on and off. Switches S1 and S2 could also be located elsewhere inthe circuit such as between the electrical contacts EC1 and node N1 andEC2 and node N2. In this case a third switch is desirable in order toopen and close a circuit between the thermistor THM and the contact TM.Switches S1 and S2 could be located intermediately in the circuitry ofthe power supply 2402, the charger control 2404 and the power supply2406 if resistor R2 is eliminated and current is sensed differently. Ineach of these cases, switches S1 and S2 in essence control whether poweris provided to electrical contacts EC1 and EC2 or whether power isremoved therefrom. Switches S1 and S2 further control whether thecontact terminals EC1 and EC2 are isolated from AC power lines or not.When isolated, a user can avoid being shocked.

[0104] The first safety switch S1 and the second safety switch S2 areselectively activated (i.e. closed, turned ON or switched ON) anddeactivated (i.e. opened, turned OFF or switched OFF) physically inresponse to respectively closing the charger door into a closed positionand opening the charger door into an open position respectively. Safetyswitches S1 and S2 correspond to the safety switch mechanisms(micro-switches 334A-334B and leaf spring switches 234A-234B) previouslydescribed. While only one of the safety switches S1 or S2 may benecessary, it is preferable that both are present so that an earthground pin is not needed and the AC power spades 201 are allowed to benon-polarized and reversible between AC hot and AC neutral whileassuring that a user does not become shocked. Additionally with thecharger door 210 in a closed position, a user is deterred from touchingthe electrical contacts EC1 and EC2 when power is supplied to them.

[0105] The rechargeable battery pack 100 includes one or morerechargeable batteries RB connected in series together to form a desiredpotential voltage, a temperature sensor opening TSO, a first batterypack terminal BT1, and a second battery pack terminal BT2. Thetemperature sensor opening TSO is preferably near a negative terminal ofan end rechargeable battery of the rechargeable batteries RB. The firstbattery pack terminal BT1 is for coupling to first electrical contactEC1 and the second battery pack terminal BT2 is for coupling to thesecond electrical contact EC2. The first and second electrical contactsEC1 and EC2 correspond to spring contacts 240A and 240B of the springloaded contact strips 238A and 238B in FIGS. 14-23 of the battery packcharger.

[0106] The present invention has many advantages over the prior art. Oneadvantage is that the one or more key slots allow differentiation of therechargeable battery pack. Another advantage to the present invention isthat the rectangular guide tabs provide backward compatibility for therechargeable battery pack so that it can be charged in former batterychargers as well as be used in former battery operated devices. Anotheradvantage to the present invention is that the rechargeable battery packhas an opening to allow a temperature sensor to probe a rechargeablebattery at its terminal casing so that it need not be embedded into therechargeable battery back and therefore lowers its cost. Anotheradvantage to the present invention is that the one or more key slots andthe one or more key tabs provide a safety mechanism to safely charge theappropriate rechargeable battery pack. Another advantage to the presentinvention is that the spring switch safety mechanism provides a safetysystem to avoid electrically shocking a user. Another advantage to thepresent invention is that the rectangular guide tabs in the battery packcharger assures that the appropriate rechargeable battery is inserted inorder to be safely charged.

[0107] The preferred embodiments of the present invention are thusdescribed. While the present invention has been described in particularembodiments, the present invention should not be construed as limited bysuch embodiments. The present invention should not be limited to theembodiments disclosed but rather construed according to the claims thatfollow below.

What is claimed is:
 1. A rechargeable battery pack comprising: aplurality of batteries coupled in series to generate electrical capacityfor a battery powered device and to receive a charging current from acharger; and a battery pack housing to house the plurality of batteries,the battery pack housing having an opening to provide access to abattery case of one of the plurality of batteries, and, a leftrectangular guide tab and a right rectangular guide tab to guide therechargable battery pack into a battery powered device or a charger. 2.The rechargeable battery pack of claim 1 wherein, the left rectangularguide tab is the first guide tab near the front of the left side of therechargeable battery pack and the right rectangular guide tab is thefirst guide tab near the front of the right side of the rechargeablebattery pack.
 3. The rechargeable battery pack of claim 1 wherein, theleft rectangular guide tab slides over a ramp of a charger latch toallow insertion into a charger and engages with a vertical face of thecharger latch to lock the rechargeable battery pack in place in thecharger.
 4. The rechargeable battery pack of claim 3 wherein, a bottomside of the left rectangular guide tab slides over the ramp of thecharger latch and a rear side of the left rectangular guide tab engageswith the vertical face of the charger latch to lock the rechargeablebattery pack in place in the charger.
 5. The rechargeable battery packof claim 1 wherein, the right rectangular guide tab slides over a rampof a right charger latch and engages with a vertical face of the rightcharger latch to lock the rechargeable battery pack in place in acharger.
 6. The rechargeable battery pack of claim 5 wherein, a bottomside of the right rectangular guide tab slides over the ramp of theright charger latch and a rear side of the right rectangular guide tabengages with the vertical face of the right charger latch to lock therechargeable battery pack in place in the charger.
 7. The rechargeablebattery pack of claim 5 wherein, the left rectangular guide tab slidesover a ramp of a left charger latch initially at a front edge andengages with a vertical face of the left charger latch to lock therechargeable battery pack in place in the charger.
 8. The rechargeablebattery pack of claim 1 wherein, the opening in the battery pack housingallows a temperature sensor of a charger to thermally couple to thebattery case of the one of the plurality of batteries.
 9. Therechargeable battery pack of claim 1 wherein, the battery case is theterminal casing of the one of the plurality of batteries and the openingin the battery pack housing allows a temperature sensor of a charger tomechanically, thermally, and electrically couple to the terminal casingof the one of the plurality of batteries.
 10. The rechargeable batterypack of claim 1 wherein, the left rectangular guide tab and the rightrectangular guide tab are respectively on a left side and a right sideand nearest a front side of the rechargeable battery pack and therechargeable battery pack further includes, a first mirrored-L shapedguide tab on the left side and a first L shaped guide tab on the rightside of the battery pack housing.
 11. The rechargeable battery pack ofclaim 10 wherein, the first mirrored-L shaped guide tab and first Lshaped guide tab are respectively nearest the middle on the left sideand the right side of the rechargeable battery pack and the rechargeablebattery pack further includes, a second mirrored-L shaped guide tab onthe left side and a second L shaped guide tab on the right side of thebattery pack housing nearest a rear side of the rechargeable batterypack.
 12. The rechargeable battery pack of claim 10 wherein, the firstmirrored-L shaped guide tab and the first L shaped guide tab engage withrectangular guide tabs of a charger to hold it in place and stop itsforward insertion into the charger.
 13. The rechargeable battery pack ofclaim 11 wherein, the left rectangular guide tab and the rightrectangular guide tab provide backward compatibility to allow therechargeable battery back to be charged by former battery pack chargersat a slow charge rate and to operate in a plurality of former batterypowered devices.
 14. The rechargeable battery pack of claim 1 furthercomprising: one or more key tabs to distinguish the rechargeable batterypack.
 15. The rechargeable battery pack of claim 1 further comprising:an edge having one or more key slots to distinguish the rechargeablebattery pack.
 16. The rechargeable battery pack of claim 15 wherein, therechargeable battery pack is distinguished from others to indicate thatit has the opening in the battery pack housing to provide access to thebattery case of the one of the plurality of batteries.
 17. Therechargeable battery pack of claim 1 further comprising: a surfacehaving one or more key slots to distinguish the rechargeable batterypack.
 18. The rechargeable battery pack of claim 15 wherein, the one ormore key slots is an elongated key slot.
 19. The rechargeable batterypack of claim 1 wherein, a first battery of the plurality of batteriescoupled in series has a first terminal case with a first terminal at oneend, a second battery of the plurality of batteries coupled in serieshas a second terminal at an opposite end, and the opening in the batterypack housing provides access to the first terminal case of the firstbattery.
 20. The rechargeable battery pack of claim 1 furthercomprising: a first contact on a right side and a second contact on aleft side to couple to a charger to charge the plurality of batteries orto couple to a battery powered device to power it with the plurality ofbatteries.
 21. The rechargeable battery pack of claim 20 wherein, thebattery pack housing has an upper half and a lower half, a front sideand a back side and, the first contact is in the upper half on the rightside near the front side and the second contact is in the upper half onthe left side near the front side.
 22. The rechargeable battery pack ofclaim 1 wherein, a first battery of the plurality of batteries coupledin series has a first terminal case with a first terminal at one end, asecond battery of the plurality of batteries coupled in series has asecond terminal at an opposite end, the opening in the battery packhousing provides access to the first terminal case of the first battery,and the rechargeable battery pack further includes, a first contact on aright side, the first contact coupled to the first terminal of the firstbattery, and a second contact on a left side, the second contact coupledto the second terminal of the second battery.
 23. The rechargeablebattery pack of claim 1 wherein, the opening is in a front side of thebattery pack housing nearer a right side, the left rectangular guide tabis in a base of a left side of the rechargeable battery pack nearer thefront side, and the right rectangular guide tab is in a base of theright side of the rechargeable battery pack nearer the front side.
 24. Abattery pack charger for charging a rechargeable battery pack, thebattery pack charger comprising: a charger housing having an opening toreceive a rechargeable battery pack; a door configured to cover theopening of the charger housing when closed; and a first safety switchmechanism.
 25. The battery pack charger of claim 24 wherein, the firstsafety switch mechanism is configured to selectively apply power to afirst contact terminal of the battery pack charger in response toopening and closing of the door.
 26. The battery pack charger of claim25 wherein, the first safety switch mechanism is activated with the doorin a closed position to apply power to the first contact terminal of thebattery pack charger and the first safety switch mechanism isdeactivated with the door in an open position to remove power from thefirst contact terminal of the battery pack charger.
 27. The battery packcharger of claim 25 wherein, the first safety switch mechanism isconfigured to be activated and deactivated to switch an AC voltage onand off into a power supply of the battery pack charger to selectivelyapply power to the first contact terminal of the battery pack charger inresponse to opening and closing of the door.
 28. The battery packcharger of claim 25 wherein, the first safety switch mechanism isconfigured to be activated and deactivated to switch a DC voltage from aDC power supply on and off to selectively apply power to the firstcontact terminal of the battery pack charger in response to opening andclosing of the door.
 29. The battery pack charger of claim 25 wherein,the first safety switch mechanism is configured to be activated anddeactivated to selectively apply a DC voltage from a DC power supplyinto the first contact terminal of the battery pack charger in responseto opening and closing of the door.
 30. The battery pack charger ofclaim 24 wherein, the first safety switch mechanism is a micro-switch.31. The battery pack charger of claim 24 wherein, the first safetyswitch mechanism is a leaf spring switch mechanism.
 32. The battery packcharger of claim 31 wherein, the leaf spring switch mechanism includes afirst spring loaded conductive strip and a first leaf spring conductivestrip, the first spring loaded conductive strip and the first leafspring conductive strip having a gap therebetween with the door beingopened, the at least one lever arm to couple to the first leaf springconductive strip upon closure of the door to close the gap and couplethe first leaf spring conductive strip to the first spring loadedconductive strip
 33. The battery pack charger of claim 32 wherein, thefirst spring loaded conductive strip couples to an AC terminal of thebattery pack charger and the first leaf spring conductive strip iscoupled to an AC input of a power supply of the battery pack charger.34. The battery pack charger of claim 32 wherein, the first springloaded conductive strip couples to one of the contact terminals of thebattery pack charger and the first leaf spring conductive strip iscoupled to a DC output of a power supply of the battery pack charger.35. The battery pack charger of claim 25 further comprising: a secondsafety switch mechanism configured to selectively apply power to asecond contact terminal of the battery pack charger, the second safetyswitch mechanism responsive to opening and closing of the door.
 36. Thebattery pack charger of claim 35 wherein, the first and second safetyswitch mechanisms are activated with the door in a closed position toapply power to the first and second contact terminals of the batterypack charger and the first and second safety switch mechanisms aredeactivated with the door in an open position to remove power from thefirst and second contact terminals of the battery pack charger.
 37. Thebattery pack charger of claim 35 wherein, the first and second safetyswitch mechanisms are configured to be activated and deactivated toswitch an AC voltage on and off into a power supply of the battery packcharger to selectively apply power to the first and second contactterminals of the battery pack charger in response to opening and closingof the door.
 38. The battery pack charger of claim 35 wherein, the firstand second safety switch mechanisms are configured to be activated anddeactivated to switch a DC voltage from a DC power supply on and off toselectively apply power to the first and second contact terminals of thebattery pack charger in response to opening and closing of the door. 39.The battery pack charger of claim 35 wherein, the first and secondsafety switch mechanisms are activated and deactivated to selectivelyapply a DC voltage from a DC power supply into the first and secondcontact terminals of the battery pack charger in response to opening andclosing of the door.
 40. The battery pack charger of claim 35 wherein,the first and second safety switch mechanisms are micro-switchesactivated and deactivated in response to opening and closing of thedoor.
 41. The battery pack charger of claim 35 wherein, the first andsecond safety switch mechanisms are leaf spring switch mechanismsactivated and deactivated in response to opening and closing of thedoor.
 42. The battery pack charger of claim 41 wherein, each of the leafspring switch mechanisms includes, a first spring loaded conductivestrip and a first leaf spring conductive strip, the first spring loadedconductive strip and the first leaf spring conductive strip having a gaptherebetween with the door being opened, the at least one lever arm tocouple to the first leaf spring conductive strip upon closure of thedoor to close the gap and couple the first leaf spring conductive stripto the first spring loaded conductive strip
 43. The battery pack chargerof claim 42 wherein, each of the first spring loaded conductive stripscouples to an AC terminal of the battery pack charger and each of thefirst leaf spring conductive strips is coupled to input AC terminals ofa power supply of the battery pack charger.
 44. The battery pack chargerof claim 42 wherein, each of the first spring loaded conductive stripscouples to one of the contact terminals of the battery pack charger andeach of the first leaf spring conductive strips is coupled to a DCoutput terminal of a power supply of the battery pack charger.
 45. Thebattery pack charger of claim 24 wherein, the inner housing includes afirst rectangular guide tab on a sidwall of the inner housing to guide arechargeable battery pack into the inner housing of the battery packcharger.
 46. The battery pack charger of claim 45 wherein, the innerhousing includes a second rectangular guide tab on a sidwall oppositethe first rectangular guide tab, the second rectangular guide tab toguide a rechargeable battery pack into the inner housing of the batterypack charger.
 47. The battery pack charger of claim 45 wherein, thefirst rectangular guide tab is positioned on the sidwall of the innerhousing to allow a rectangular tab on a rechargeable battery pack toslide under and to catch an L shaped tab to prevent further insertion ofa rechargeable battery pack into the inner housing of the battery packcharger.
 48. The battery pack charger of claim 47 wherein, the firstrectangular guide tab catches a first L shaped tab of a rechargeablebattery pack to differentiate recharegable batttery packs that can besafely charged from those that can not be safely charged.
 49. Thebattery pack charger of claim 45 wherein, the first rectangular guidetab is positioned on the sidwall of the inner housing to allow arectangular tab on a rechargeable battery pack to slide under and tocatch an mirrored-L shaped tab to prevent further insertion of arechargeable battery pack into the inner housing of the battery packcharger.
 50. The battery pack charger of claim 49 wherein, the firstrectangular guide tab catches a first mirrored-L shaped tab of arechargeable battery pack to differentiate recharegable batttery packsthat can be safely charged from those that can not be safely charged.51. The battery pack charger of claim 46 wherein, the first and secondrectangular guide tabs are positioned on the sidwalls of the innerhousing to allow a pair of rectangular tabs on a rechargeable batterypack to slide under and to catch an L shaped tab and an mirrored-Lshaped tab respectively to prevent further insertion of a rechargeablebattery pack into the inner housing of the battery pack charger.
 52. Thebattery pack charger of claim 49 wherein, the first and secondrectangular guide tabs catch a first L shaped tab and a first mirrored-Lshaped tab of a rechargeable battery pack on opposite sides todifferentiate recharegable batttery packs that can be safely chargedfrom those that can not be safely charged.
 53. The battery pack chargerof claim 24 further comprising: one or more key tabs configured to matewith one or more key slots of a rechargeable battery pack in order todistinguish it from other rechargeable battery packs.
 54. The batterypack charger of claim 24 wherein, the charger housing has one or morekey slots to mate with one or more key tabs of a rechargeable batterypack in order to distinguish it from other rechargeable battery packs.55. The battery pack charger of claim 25 further comprising: a powersupply coupled to the first safety switch mechanism to selectivelyreceive an AC voltage and selectively apply DC power to the firstcontact terminal.
 56. The battery pack charger of claim 55 wherein, thepower supply selectively applies a DC power having a DC current of aslow charge rate.
 57. The battery pack charger of claim 55 wherein, thepower supply selectively applies a DC power having a DC current of afast charge rate.
 58. The battery pack charger of claim 55 wherein, thepower supply is a switching power supply.
 59. The battery pack chargerof claim 55 wherein, the power supply is a linear power supply.
 60. Thebattery pack charger of claim 35 further comprising: a power supplycoupled to the first and second safety switch mechanisms to selectivelyreceive an AC voltage and selectively apply DC power to the first andsecond contact terminals.
 61. The battery pack charger of claim 60wherein, the power supply selectively applies a DC power having a DCcurrent of a slow charge rate.
 62. The battery pack charger of claim 60wherein, the power supply selectively applies a DC power having a DCcurrent of a fast charge rate.
 63. The battery pack charger of claim 60wherein, the power supply includes a non-isolation transformer.
 64. Thebattery pack charger of claim 60 wherein, the power supply is aswitching power supply.
 65. The battery pack charger of claim 60wherein, the power supply is a linear power supply.
 66. The battery packcharger of claim 24 further comprising: a temperature sensor configuredto thermally couple to a rechargeable battery of a rechargeable batterypack to measure a temperature of the rechargeable battery.
 67. Thebattery pack charger of claim 66 wherein, the temperature sensor isconfigured to thermally couple to the rechargeable battery through anopening in the rechargeable battery pack.
 68. The battery pack chargerof claim 66 wherein, the temperature sensor measures temperature of therechargeable battery in the rechargeable battery pack to safely controlat least one fast charge rate of the battery pack charger.
 69. Thebattery pack charger of claim 24 further comprising: a catch mechanismto allow insertion of a rechargeable battery pack into the battery packcharger and to hold it in place.
 70. The battery pack charger of claim69 wherein, the catch mechanism includes a first catch to engage with afirst rectangular tab of a rechargeable battery pack.
 71. The batterypack charger of claim 70 wherein, the catch mechanism further includes asecond catch opposite the first to engage with a second rectangular tabof a rechargeable battery pack opposite the first rectangular tab. 72.The battery pack charger of claim 70 wherein, the first catch of thecatch mechanism further is ramp shaped from a rear side to engage with afront edge of the first rectangular tab to allow initial insertion andthe first catch has a vertical surface on a front side to engage with arear side of the first rectangular tab to hold the rechargeable batterypack in place.
 73. The battery pack charger of claim 70 wherein, thecatch mechanism further includes a release button that upon depressionby a user releases the hold of the catch mechanism to allow extractionof a rechargeable battery pack from the battery pack charger.
 74. Thebattery pack charger of claim 73 wherein, the catch mechanism furtherincludes a spring and a spring arm and when the release button isdepressed by a user it retracts the catch mechanism into a surface ofthe inner housing to allow a rectangular tab of a rechargeable batterypack to slide by to extract it from the battery pack charger.
 75. Thebattery pack charger of claim 24 wherein, the first safety switchmechanism is configured to open a first circuit in response to the doorbeing in an open position to avoid power being applied to a firstcontact terminal of the battery pack charger.
 76. The battery packcharger of claim 75 wherein, the first safety switch mechanism isfurther configured to close the first circuit in response to the doorbeing in a closed position.
 77. The battery pack charger of claim 75further comprising: a second safety switch mechanism configured to opena second circuit in response to the door being in an open position toavoid power being applied to a second contact terminal of the batterypack charger.
 78. The battery pack charger of claim 78 wherein, thefirst and second safety switch mechanisms are further configured toclose the first and second circuits in response to the door being in aclosed position.
 79. The battery pack charger of claim 78 furthercomprising: a third safety switch mechanism configured to open a thirdcircuit in response to the door being in an open position to avoid powerbeing applied to a third contact terminal of the battery pack charger,and wherein, the first contact terminal of the battery pack charger is apositive contact terminal configured to couple to a positive terminal ofa rechargeable battery pack, the second contact terminal of the batterypack charger is a negative contact terminal configured to couple to anegative terminal of a rechargeable battery pack, and the third contactterminal of the battery pack charger is a temperature sensing terminalconfigured to couple to a temperature sense terminal of a rechargeablebattery pack.
 80. A method of constructing a rechargeable battery pack,the method comprising: forming a top half and a bottom half of a batterypack housing, the battery pack housing having an opening in a front sideto allow insertion of a temperature probe, and a pair of openings on aright and left side to allow protrusion of a pair of contact terminals,the bottom half having a pair of rectangular guide tabs near a frontside on the left and right sides to couple the rechargeable battery packinto a battery pack charger or a battery powered device; coupling aplurality of rechargeable batteries in series together, a firstrechargeable battery of the series having a terminal coupled to one ofthe pair of contact terminals, a last rechargeable battery of the serieshaving an opposite terminal coupled to the other one of the pair ofcontact terminals; inserting the plurality of rechargeable batteriesinto the battery pack housing so that the terminal casing of the firstrechargeable battery of the series is contactable by a temperature probethrough the opening in the front side of the battery pack housing andthe pair of contact terminals protrude through the pair of openings onthe left and right side; and fusing the top half and the bottom half ofthe battery pack housing together to hold the plurality of rechargeablebatteries coupled in series together within the rechargeable batterypack.
 81. The method of claim 80 of constructing a rechargeable batterypack wherein, the battery pack housing further has a first L shapedguide tab near a middle of the right side and a first mirrored-L shapedguide tab near a middle of the left side.
 82. The method of claim 81 ofconstructing a rechargeable battery pack wherein, the battery packhousing further has a second L shaped guide tab near a near side on theright side and a second mirrored-L shaped guide tab near the rear sideon the left side.
 83. The method of claim 80 of constructing arechargeable battery pack wherein, the battery pack housing further hasone or more key slots in a top rear edge to differentiate therechargeable battery pack as being safe for fast charging by a batterypack charger.
 84. The method of claim 80 of constructing a rechargeablebattery pack wherein, the one or more key slots is an elongated key slotin the top rear edge.
 85. The method of claim 80 of constructing arechargeable battery pack wherein, the battery pack housing providesbackward compatibilty by coupling to former battery pack chargers andformer battery powered devices.
 86. A method of differentiatingrechargeable battery packs by a battery pack charger, the methodcomprising: providing the battery pack charger with an inner housing foraccepting a rechargeable battery pack, a door to enclose an opening intothe inner housing and a safety switch mechanism responsive to operationof the door, and one or more key tabs; providing the rechargeablebattery pack, the rechargeable battery pack having one or more keyslots; inserting the rechargeable battery pack into the battery packcharger; and closing the door of the battery pack charger on therechargeable battery pack and determining if the one or more key tabsmate and engage with the one or more key slots in the rechargeablebattery pack to further determine if the safety switch mechanism shouldswitch on in response to the door being closed and cause the batterypack charger to charge the rechargeable battery pack.
 87. The method ofclaim 86 of differentiating rechargeable battery packs in a battery packcharger wherein, the one or more key tabs do not mate and engage withthe one or more key slots in the rechargeable battery pack so that thedoor does not close, and in response, the safety switch mechanism doesnot switch on to charge the rechargeable battery pack.
 88. The method ofclaim 86 of differentiating rechargeable battery packs in a battery packcharger wherein, the one or more key tabs do mate and engage with theone or more key slots in the rechargeable battery pack so that the doorcloses, and in response, the safety switch mechanism switches on tocharge the rechargeable battery pack.
 89. The method of claim 86 ofdifferentiating rechargeable battery packs in a battery pack chargerwherein, the inner housing of the battery pack charger has left andright rectangular guide tabs on left and right side walls; and theinserting of the rechargeable battery pack into the battery pack chargerdetermines if the rechargeable battery pack being inserted has left andright rectangular guide tabs on left and right sides respectivelynearest a front side to slide under the left and right rectanglularguide tabs on the left and right side walls of the battery pack chargerto be safely charged therein.
 90. The method of claim 86 ofdifferentiating rechargeable battery packs in a battery pack chargerwherein, the rechargeable battery pack does not have left and rightrectangular guide tabs on left and right sides respectively nearest afront side and can not slide under the left and right rectanglular guidetabs on the left and right side walls of the battery pack charger andcan not be safely charged therein.
 91. The method of claim 86 ofdifferentiating rechargeable battery packs in a battery pack chargerwherein, the rechargeable battery pack does has left and rightrectangular guide tabs on left and right sides respectively nearest afront side and slides under the left and right rectanglular guide tabson the left and right side walls of the battery pack charger to besafely charged therein.
 92. A battery pack charger for distinguishingrechargeable battery packs, the battery pack charger comprising: acharger housing having an opening to receive a rechargeable battery packinto an inner housing; and a first rectangular guide tab on a firstsidwall of the inner housing to guide a rechargeable battery pack intothe inner housing of the battery pack charger.
 93. The battery packcharger of claim 92 wherein, the first rectangular guide tab ispositioned on the sidwall of the inner housing to allow a rectangulartab on a first rechargeable battery pack to slide under for completeinsertion and to catch an L shaped tab on a second rechargeable batterypack to prevent further insertion of it into the inner housing of thebattery pack charger, the first rectangular guide tab catches a first Lshaped tab to differentiate recharegable batttery packs that can besafely charged from those that can not be safely charged.
 94. Thebattery pack charger of claim 92 wherein, the first rectangular guidetab is positioned on the sidwall of the inner housing to allow arectangular tab on a first rechargeable battery pack to slide under forcomplete insertion and to catch a mirrored-L shaped tab on a secondrechargeable battery back to prevent further insertion of it into theinner housing of the battery pack charger.
 95. The battery pack chargerof claim 92 further comprising: a second rectangular guide tab on asecond sidwall of the inner housing opposite the first rectangular guidetab, the second rectangular guide tab to guide a rechargeable batterypack into the inner housing of the battery pack charger.
 96. The batterypack charger of claim 95 wherein, the first and second rectangular guidetabs are positioned on the sidwalls of the inner housing to allow a pairof rectangular tabs of a first rechargeable battery pack to slide underfor complete insertion and to catch an L shaped tab and a mirrored-Lshaped tab of a second rechargeable battery pack to prevent furtherinsertion of it into the inner housing of the battery pack charger. 97.The battery pack charger of claim 95 wherein, the first and secondrectangular guide tabs catch a first L shaped tab and a first mirrored-Lshaped tab to differentiate recharegable batttery packs that can besafely charged from those that can not be safely charged.
 98. Thebattery pack charger of claim 92 further comprising: a door configuredto cover the opening of the charger housing when closed and to prohibitcharging of a rechargeable battery pack when open, the door having oneor more key tabs on an inside surface.
 99. The battery pack charger ofclaim 92 further comprising: one or more key tabs to distinguishrechargeable battery packs by mating with one or more key slots of arechargeable battery pack to allow it to be fully inserted and the doorto close into a closed postion for it to be charged.
 100. The batterypack charger of claim 98 wherein, the one or more key tabs is anelongated key tab.
 101. The ornamental design for a rechargeable batterypack, substantially as shown and described.